Reversible inhibition of sperm under guidance
Reversible Inhibition of Sperm Under Guidance (RISUG), formerly referred to as SMA, is the development name of a male contraceptive developed at IIT (Delhi) in India by Dr. Sujoy K Guha. It is currently undergoing Phase III clinical trials in India. It has been patented in India, China, Bangladesh and the United States.
Mechanism of action
RISUG works by an injection into the vas deferens, the vessel through which the sperm moves before ejaculation. In a matter of minutes, the injection coats the walls of the vas with a clear gel made of 60 mg of the copolymer styrene/maleic anhydride (SMA) with 120 µL of the solvent dimethyl sulfoxide. The copolymer is made by irradiation of the two monomers with a dose of 0.2 to 0.24 megarad for every 40 g of copolymer and a dose rate of 30 to 40 rad/s. The source of irradiation is cobalt-60 gamma radiation.
The effect the chemical has on sperm is not completely understood. Originally it was thought that it lowered the pH of the environment enough to kill the sperm. More recent research claims that this is not enough to explain the effect.
One explanation is that the polymer is an anhydride, and hydrolizes in the presence of water in the spermatic fluid. Due to the breaking of a cyclic group, the polymer becomes a hydride and has a positive charge. This disturbs the negative charge of the sperm membrane on contact. (From U.S. Patent 5,488,075)
Some theorize that the polymer surface has a negative and positive electric charge mosaic. The differential charge from the gel ruptures the sperm's cell membrane as it passes through the vas, stopping the sperm before they can start their journey to the egg.
"Within an hour, the drugs produce an electrical charge that nullifies the electrical charge of the spermatozoa, preventing it from penetrating the ovum," Dr. Guha said.
- It works - Of all the men who've had the RISUG injection (and 15 of the 250 had it more than 10 years ago), there has been only one unplanned pregnancy among their partners — and in that instance, the injection wasn't administered properly.
- Convenient - Neither sexual partner has to interrupt the throes of passion to use it — no more running to the bathroom and fumbling with various ointments and plastics.
- Non-surgical - The process, once it is refined and approved, will be operation-free. Men can leave the hospital immediately after an injection and resume their normal sex lives within a week.
- Long-lasting - According to Guha, a single 60 mg injection can be effective for at least 10 years.
- Few side effects - After testing RISUG on more than 250 volunteers, neither Guha nor other researchers in the field claim side effects more worrisome than a slight scrotal swelling in some men immediately following the injection which goes away after a few weeks, though there are also unconfirmed reports of kidney problems. These drawbacks, however, pale in comparison with those of contraceptive pills, which can cause health problems ranging from severe migraines to blood clots.
- Reversible - The contraceptive appears to be reversible by flushing the vas deferens with another injection of dimethyl sulfoxide or sodium bicarbonate solution. (The sodium bicarbonate solution cannot be used as the solvent in the initial injection since it would neutralize the positive charge effect.) To date, reversing the procedure has been tried only on non-human primates, but among them, it's been reversed successfully multiple times.
The thoroughness of carcinogenicity, teratogenicity and toxicity testing in clinical trials has been questioned. In October 2002, India's Ministry of Health aborted the clinical trials due to reports of albumin in urine and scrotal swelling in Phase III trial participants.  The Indian Council for Medical Research noted that dimethyl sulfoxide used as a solvent for the injection is known to cause kidney damage.  Although the ICMR has reviewed and approved the toxicology data three times, some United States researchers say that the studies were not done according to recent international standards.
RISUG was resubmitted for a new round of tests at a US lab, and was approved as non-mutagenic in July 2005. With this new stamp of approval, the path to continued Phase III trials in India became clear.
In March 2006, the ICMR announced that Phase III trials of RISUG could resume at 4 centers around India. The announcement of this progress led to renewed interest in RISUG. Unfortunately, little progress has been made since March. The research centers do not have enough of the RISUG compound to move forward with the trial. Marksans, the pharmaceutical company which has a manufacturing agreement with the inventor and the government, is now over a year past its initial April 2005 product delivery estimate. It is not clear why the delay continues.
Once this form of contraception is released into the market, it could displace the use of condoms. Unlike condoms, RISUG provides no protection against the spread of sexually transmitted diseases. A study, however, is underway to test the efficacy of RISUG as an anti-HIV agent, due to a hypothesis that the styrene maleic acid lowers pH to a level sufficient to destroy HIV in semen. 
- U.S. Patent 5,488,075
- Detailed information from Male contraceptives.org
- Studies of RISUG Experimental male contraceptive 1976-2004
- ICMR Website
- ICMR 2004 Anuual Report
- Hindustan Times
- The Sperminator in Grist Magazine
- India Today Article
- Indian Express Article
- Canadian Doctor implements RISUG